1. Field of the Invention
The invention relates to a process for whole grain conditioning, especially of brewer's grains, such as malted barley, and the processing of these whole grain-conditioned cereal grains in the brewing technology.
2. Discussion of Background Information
Brewer's grains are mechanically broken up, e.g. by crushing in roller, hammer or corundum-disk mills or in rotor-stator systems, prior to further processing in the brewing process. Where roller mills are used, it is known in the prior art to wet the brewer's grains in conditioning screw conveyors to a max. of 2% moisture content to improve the milling result; while in so-called “soft conditioning” mills, a water component of up to 16% is introduced to the malt in a so-called “softening shaft.” In both systems the holding time of the malt in the wetting zone is somewhere around 60 sec. This holding time is not sufficient to allow the malt to fully absorb the water, and at least part of the introduced water is left still clinging to the husk in its free state. Because of this short holding time, and also the naturally occurring dissimilar grain sizes of the cereal grain, a homogenous water uptake in the charge is not ensured.
As the proportion of introduced water increases, there is an increased danger of the rollers of the mills sticking and/or of problems arising in connection with hygiene.
In the subsequent mashing process, there takes place the enzymatic conversion of water-insoluble, large molecular weight constituents such as starches and proteins to smaller molecular weight, water-soluble substances, e.g. sugar and amino acids. In order to convert and extract these from the cereal grains, the mechanical preparation of the brewer's grains has to have been done sufficiently.
In the subsequent lautering process, the resulting solution (mash) is separated into the liquid phase (wort) and the solid substances (draff).
In the brewing technology generally a lauter tun or a mash filter is used for the separation of solid/liquid.
In the lauter tun, the solid, water-insoluble parts of the cereal grain, the husks, form a filter layer, through which the liquid (wort) is drawn downwards and filtered. If due to insufficient elasticity the husks and germ are broken up into too small a size in the coarse grinding, then firstly, an increased dissolution can lead to unwanted constituents such as polyphenols, lipids, etc. getting into the wort, and furthermore it results in a pronounced negative effect on the structure of the filter layer, leading to a slowing down of the lautering of the wort.
In the mash filter, the effect that unbroken whole husks have on the speed of lautering is of little importance due to the low height of the filter layer.
In DE-A-4440481 the suggestion was therefore made to first wet the malt, and then subject it to a pressure treatment in the milling gap, and also to separate the husks and endosperm by sieving. For this the malt mill used is fitted with at least one sieve. The separated husks are then subjected to an impact treatment so that any extract still adhering to them can be removed.
By impacting, not only can a gain in extract be obtained, it also increases the volume of the husk fraction. This increased fraction produces an optimized filter bed in the lauter tun which in turn ensures an improved lautering; or conversely it is possible to use a smaller portion of the husks as filter material, by which the possible entry of polyphenols is reduced.
Also known are a coarse grinding mill for malt with a continuous monitoring of the grinding (DE-A-10218424), a wet coarse grinding (DE-A-10255504 among others), an enclosed, airless coarse grinding (DE-A-19740036), or an extrusion of malt grist (DE-A-3212390).